In the field of semiconductor devices, the device density is increased and the device dimension is reduced, continuously. The demand for the packaging or interconnecting techniques in such high density devices is also increased to fit the situation mentioned above. Conventionally, in the flip-chip attachment method, an array of solder bumps is formed on the surface of the die after the re-distribution layer be formed. The formation of the solder bumps may be carried out by using a solder composite material through a solder mask for producing a desired pattern of solder bumps. The function of chip package includes power distribution, signal distribution, heat dissipation, protection and support, and so on. As a semiconductor become more complicated, the traditional package technique, for example lead frame package, flex package, rigid package technique, can't meet the demand of producing smaller chip with high density elements on the chip. The trend of package technique is toward ball grid array (BGA), flip chip ball grid array (FC-BGA), chip scale package (CSP), wafer level package (WLP) today.
Image sensors have become widely used in digital still cameras, cellular phones, automobile, and other applications. The technology used to manufacture image sensors, and in particular CMOS image sensors, has continued to advance at great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of the image sensor. In a large number of image sensors, a photodiode structure called a pinned or a buried photodiode is used because of its low noise performance. In this photodiode structure, a P+ layer is implanted at or below the surface of the photodiode adjacent to a transfer gate. An N− layer is implanted deeper into the silicon substrate. This is the buried layer that stores charge away from the surface region, and thus, away from defects at the surface of the silicon substrate. The purpose of the P+ layer is to provide a photodiode with increased storage capacitance and to passivate the defects on the photodiode surface.
Various structures using flip-chip mounting of an image sensor chip have been developed in an attempt to simplify the construction of image sensor packages. U.S. Pat. No. 6,144,507 discloses an image sensor chip mounted directly to a printed circuit board (PCB). An image sensor chip is mounted in flip-chip fashion over an aperture within the PCB, and a transparent cover is either attached directly to the active surface of the chip or bonded to the side of the PCB opposite that to which the image sensor chip is attached and over the aperture. Although these methods eliminate the difficulties associated with wire bonding, however, the PCB's is very large with respect to the size of the image sensor chip and the transparent cover.
U.S. Pat. No. 5,786,589 disclosed the features of bonding a TAB sheet to a glass substrate and bonding an image sensor chip to the TAB tape with a conductive film. This design requires a specialized substrate attachment technique due to the TAB-type connection leads. Moreover, the conductive film risks interference with sensing circuitry on the image sensor chip and requires the formation of dummy leads or dam structures to compensate for this problem.
U.S. Pat. No. 6,885,107 disclosed conventional type image sensor package. It employed a BGA package which includes a plurality of ball under the substrate and the die is exposed outside of the substrate. In accordance with the present invention, image sensor packaging having the above-described and other beneficial characteristics and methods for fabrication thereof are provided. An image sensor chip is flip-chip mounted to conductive traces on a first surface of a transparent substrate. The active surface of the image sensor chip is protected from contamination after mounting by depositing a bead of sealant around the periphery of the image sensor chip between the active surface of the image sensor chip and the first surface of the substrate, thus eliminating any need for additional damming structures or spacing frames as used in the prior art. Discrete conductive elements such solder balls or columns are attached to ends of the conductive traces which form an array pattern, the discrete conductive elements extending transversely from the conductive traces on the first surface to a substantially common plane at a level beyond a back surface of the image sensor chip. The resulting structure comprises a board-over-chip (BOC) package arrangement. Thus, the thickness of the substrate is unlikely to be scaled down due to the structure has ball high and extruding die receiving structure which limits the scale of the package shrinkage.
The prior arts suffer complicated processes to form the image package and the package structure is unable to be scaled down. Further, these prior arts only disclosed single chip package, no multiple chip structure is illustrated. Therefore, based-on the shortcomings of there prior arts, the present invention provide a semiconductor device package manufactured by simpler processes, with better reliability.